For one portion of my Kinect hacking project I would like to create a row of fans that can be turned on and off with your hand. When a user moves around the room, the fans that are closest to the user will turn on and when the user moves away the fans stop.

I knew that I wanted to use an Arduino for this project so that I can communicate to my Kinect via serial communication. My first issue was finding a way to control multiple motors from one arduino. From the arduino website I knew that digital out pins could never provide enough current to power and switch the motors so I knew I would need to get some external power going. In order to separate the power from the arduino and the fans I used standard 5v relays to act as switches. On one side I have power from a power supply and on the other I use a digital out pin to energize the coil inside the relay, this way there is no problem with current and multiple motors would work just as well.

This turned out to work great and to make the board nicer looking I added two LEDs as status indicators.

Here is a video of one motor with an relays. My next task will be building this x20

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*UPDATE*

After connecting my second relay to my arduino I quickly realize that the arduino does not have enough current to open two or more relays at the same time. The solution to this was very anoying, but very simple. All you need to do is add a n2222 transistor before the relay and everything should work perfectly fine. Here is two fans working.